Revealing mistake: In the opening shot of the Washington Monument, the monument is very noticeably shaking left and right as the camera pans up (likely indicating that the monument and the background are a composite image). (00:01:00)
Audio problem: When Storm says "I command the Sahara Winds," her mouth is completely still for the last two words. (00:04:00)
Continuity mistake: When Storm throws her communicator and the portal-opening orb on the ground for the other X-Men to find, they land right next to each other. When Jubilee finds the communicator, the orb is missing until the shot changes. (00:06:40 - 00:08:10)
Audio problem: When Wolverine says "Now move over!", you can see his reflection in the truck's windshield and his mouth is completely closed. (00:07:00)
Continuity mistake: When Wolverine picks up the orb, the collar of Jubilee's shirt is yellow when it should be pink. (00:08:15)
Continuity mistake: When the X-Men are examining the orb in Beast's lab, the screen for the computer monitor has become shattered in one shot for no apparent reason. (00:08:55)
Continuity mistake: When the robot blasts Cyclops in the arm, you can see that his uniform tears. The tear has instantly mended itself in the next shot. (00:13:10)
Audio problem: When Jubilee says "I think," her lips are completely pressed together for the word "think." Saying "think" would require a person to touch their tongue to their teeth and lips apart. (00:13:15)
Audio problem: When Cyclops says "I hope they weren't from the Chamber of Commerce," his mouth is completely closed. (00:14:50)
Continuity mistake: The character that says "We are saved" suddenly has gray-colored skin in the next shot. (00:18:00)
Continuity mistake: In the wide shot of Arkon, Storm and the other X-Men approaching the crowd, Cyclops' face turns black. (00:18:10)
Audio problem: When Jubilee says "But look, I think that Arkon guy really likes Storm," her mouth is completely closed for the words "I think that Arkon." (00:18:40)
Character mistake: Arkon asks Storm to rule by his side as Empress. After she agrees, he introduces her to the crowd as Queen. (00:19:10 - 00:19:45)
Answer: Chris Potter, the original Gambit voice actor, did indeed quit the role in the 4th season. His last episode was The Phalanx Covenant Part 1 so it seems reasonable that Fox would limit the use of the character even though it was recast. It doesn't appear that Potter left the role due to animosity, he stated in an interview that he wished to play Gambit in the first live action X-Men film.
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